Klette, Gisela2008-08-212008-08-212002Communication and Information Technology Research Technical Report 113, (2002)1178-3632http://hdl.handle.net/2292/2852You are granted permission for the non-commercial reproduction, distribution, display, and performance of this technical report in any format, BUT this permission is only for a period of 45 (forty-five) days from the most recent time that you verified that this technical report is still available from the original CITR web site; http://citr.auckland.ac.nz/techreports/ under terms that include this permission. All other rights are reserved by the author(s).There are hundreds of publications on different aspects of image deformations that preserve topological properties of the original binary image. The notion of a "simple pixel" is of fundamental importance for these transformations. Simple pixels in 2D binary images have been characterized in a number of ways. This paper reviews some of these characterizations and it points out that some of them are actually equivalent.Copyright CITR, The University of Auckland. You are granted permission for the non-commercial reproduction, distribution, display, and performance of this technical report in any format, BUT this permission is only for a period of 45 (forty-five) days from the most recent time that you verified that this technical report is still available from the original CITR web site under terms that include this permission. All other rights are reserved by the author(s).https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htmTechnical ReportFields of Research::280000 Information, Computing and Communication Sciences